Use your thesis statement to identify keywords for a literature search. First, identify the concepts that must be present in your topic. For example, if your thesis statement is "High wages in antebellum America encouraged the adoption of labour saving technologies that ushered in a period of rapid economic growth", key concepts are high wages, adoption of labour saving technologies, and antebellum America. Other keywords might identify demographics, etc.
Once you have your key concepts, list synonyms for each. For example, some papers may use high cost of labour instead of high wages. You might use United States instead of America, and use dates instead of the word antebellum
Combine these keywords into a search. Put all synonyms in a set of parentheses separated by OR (this must be capitalized). Outside of the parentheses, use AND to connect concepts. If any of your keywords is more than one word, enclose the phrase in quotation marks.
As you search, you may modify your keywords as you discover other terms used in the scholarly literature, or even add or modify your concepts based on new discoveries.